Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/20—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances liquids, e.g. oils
  • H01B3/22—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances liquids, e.g. oils hydrocarbons

Definitions

• This invention relates to uninhibited electrical oils, including transformer oils.
• Electrical insulating oils are sometimes formulated by adding synthetic oxidation inhibitors such as di-t-butyl-p-cresol or di-t-butyl phenol. To meet certification requirements in some jurisdictions, synthetic oxidation inhibitors can not be employed. Oils formulated without such synthetic inhibitors are sometimes referred to as "uninhibited" electrical oils. References relating to synthetically inhibited or uninhibited electrical insulating oils include U.S. Patent Nos. 3,932,267 (Lewis et al.), 4,018,666 (Reid et al.), 4,062,791 (Masunaga et al. '791), 4,070,297 (Masunaga et al.
• the present invention provides, in one aspect, a method for making an uninhibited electrical insulating oil comprising blending severely hydrotreated naphthenic distillate base oil having a viscosity of from about 50 to about 80 SSU at 38° C (100° F) and an aniline point from about 63° to about 84° C (from about 145° and about 180° F) with solvent extracted, non- hydrogenated paraffmic distillate having at least 9.0 wt. % aromatic content to provide a blend that meets one or more of EEC 60296 (Ed. 3.0 b:2003), ASTM D 3487 (2000) or BS 148:2003.
• the invention provides, in another aspect, an uninhibited electrical insulating oil comprising a blend of severely hydrotreated naphthenic distillate base oil having a viscosity of from about 50 to about 80 SSU at 38° C and an aniline point from about 63° to about 84° C with solvent extracted, non- hydrogenated paraffinic distillate having at least 9.0 wt. % aromatic content.
• the invention provides, in yet another aspect, an electrical article having a sealed housing surrounding one or more electrical devices or conductors bathed in an uninhibited electrical insulating oil comprising a blend of severely hydrotreated naphthenic distillate base oil having a viscosity of from about 50 to about 80 SSU at 38° C and an aniline point from about 63° to about 84° C with solvent extracted, non-hydrogenated paraffinic distillate having at least 9.0 wt. % aromatic content.
• non- hydrogenated refers to distillates that have not been hydrofinished, hydrotreated, hydrogenated in the presence of a catalyst or otherwise subjected to a treatment process that materially increases the distillate hydrogen content.
• a variety of naphthenic crudes may be employed to make the disclosed base oil. The crude is fractionated to provide a distillate having a suitable flash point, boiling range and viscosity. For base oils used in transformers the distillate open cup flash point may for example be greater than about 146° C (295° F), or may be greater than about 149° C (300° F).
• the boiling range for such base oils may for example be between about 204° C (400° F) and about 388° C (730° F).
• the viscosity is from about 50 to about 80 SSU at 38° C, for example from about 55 to about 65 SSU at 38° C.
• the distillate is severely hydrotreated to provide a base oil having an aniline point from about 63° to about 84° C, for example from about 71 ° to about 77° C (from about 160° F to about 170° F).
• the hydrotreating conditions preferentially will employ a bi-metallic catalyst, relatively low space velocity, relatively high hydrogen pressure and relatively high hydrogen consumption. Recommended hydrotreating conditions are shown below in Table 1 :
• the resulting base oil may for example contain about 10 to about 50 wt. %, or about 25 to about 40 wt. % aromatic hydrocarbons, as measured using ASTM D 2007 clay-gel analysis.
• suitable base oils are commercially available, including L-Series Grade 60, B-Series Grade 60 and CROSS TRANSTM 306 oils from Cross Oil Refining and Marketing, Inc.;
• Base oils that do not themselves meet the stated viscosity or aniline point requirements may be blended with one another to provide a base oil that does meet such requirements.
• HYDROCALTM 38 and HYDROCAL 100 base oils from Calumet Lubricants Co. respectively have viscosities less than 50 and greater than 80 SSU at 38° C, but may be blended to provide a base oil with a viscosity from about 50 to about 80 SSU at 38° C.
• Product specifications for an exemplary severely hydrotreated naphthenic distillate base oil are shown below in Table 2.
• a variety of paraffinic crudes may be employed to make the disclosed paraffinic distillate.
• the crude is fractionated to provide a distillate having a suitable flash point, boiling range and viscosity.
• the distillate open cup flash point may for example be greater than about 146° C (295° F), or may be greater than about 149° C (300° F).
• the boiling range for such base oils may for example be between about 204° C (400° F) and about 388° C (730° F).
• the viscosity may for example be less than about 100 SSU at 38° C, about 85 SSU at 38° C, or about 70 SSU at 38° C.
• the distillate is solvent extracted using aromatic-selective solvents and processing conditions that will be familiar to those skilled in the art.
• exemplary solvents include phenol, N-methylol pyrrolidinone ("NMP") and furfural.
• Exemplary processing conditions include temperatures of about 49° C to about 93° C (about 120° to about 200° F) and solvent to oil ratios of about 1 : 1 to about 2:1.
• the aromatic content of the extract is more than 9 wt. % as measured using ASTM D 2007 clay-gel analysis.
• the aromatic content may be about 10 to about 30 wt. %, or about 15 to about 30 wt. % of the total paraffinic distillate weight.
• the severely hydrotreated naphthenic base oil and solvent extracted paraffinic distillate may be mixed in any convenient fashion, for example by adding the paraffinic distillate to the naphthenic base oil as a blendback oil.
• the base oil and paraffinic distillate may be mixed in a variety of ratios. The chosen mixing ratio can readily be selected by persons skilled in the art, and may depend in part on the chosen oils and their viscosities and on whether compliance with all or only some of the IEC 60296, ASTM D 3487 and BS 148:2003 specifications is sought.
• the mixing ratio of naphthenic base oil to paraffinic distillate may for example be as high as 98/2, 95/5 or 90/10, and as low as 60/40, 70/30, 75/25 or 80/20.
• Extenders and other additives may be added to the blend if desired.
• napthenic base oils that do not themselves meet the stated viscosity or aniline point requirements, and paraffinic distillates that do not have the recited aromatic content may be added as extenders.
• Other suitable additives will be familiar to those skilled in the art, including pour point depressants, metal passivators and the like.
• the blend may be dried, filtered, packaged and otherwise processed using techniques that will be familiar to those skilled in the art.
• the blend may be used in a wide variety of electrical articles that will be familiar to those skilled in the art.
• Such articles typically will include a sealed housing equipped with an access port through which the disclosed electrical insulating oil may be added, replenished or replaced, and will contain one or more electrical devices or conductors bathed in the electrical insulating oil.
• Representative electrical articles include transformers, switches, circuit breakers, regulators, controls, overhead and buried cables, power supplies and motors.
• the blend desirably is formulated to meet one or more of IEC 60296, ASTM D 3487 or BS 148:2003, shown below in Table 5. Where both ASTM and ISO or IEC test methods are listed for a particular property, the ASTM test method is used for measurements relating to the ASTM D 3487 specification and the ISO or IEC test methods are used for measurements relating to the IEC 60296 and BS 148 specifications:
• Blends were prepared by combining the severely hydrotreated naphthenic distillate base oil shown in Table 2 with the solvent extracted, non- hydrogenated paraffinic distillate shown in Table 3, at 95/5 (Example 1),
• Example 2 90/10 (Example 2) and 80/20 (Example 3) mixing ratios.
• the Example 1 and Example 2 blends met the requirements of IEC 60296, ASTM D 3487 and BS 148:2003.
• the Example 3 blend met the requirements of ASTM D 3487, and it appeared that a 75/25 blend would likely do so as well.
• the Example 3 blend met the IEC 60296 oxidation stability requirements (IEC 61125) but did not meet the EEC 60296 -30 0 C viscosity requirement (ISO 3104).
• Example 4 Using the method of Example 1 , blends were prepared by combining the severely hydrotreated naphthenic distillate base oil shown in Table 2 with the solvent extracted, non-hydrogenated paraffinic distillate shown in Table 4, at 95/5 (Example 4), 90/10 (Example 5) and 80/20 (Example 6) mixing ratios.
• the Example 4 and Example 5 blends met the requirements of IEC 60296, ASTM D 3487 and BS 148:2003.
• the Example 6 blend met the requirements of ASTM D 3487, and it appeared that a 75/25 blend would likely do so as well.
• the Example 6 blend met the IEC 60296 oxidation stability requirements (IEC 61125) but did not meet the IEC 60296 - 30 0 C viscosity requirement (ISO 3104).
• Comparison Example 1 A blend was prepared by combining 80 parts of the severely hydrotreated naphthenic distillate base oil shown in Table 2 with 20 parts of CONOSOLTM 260 oil from Penreco Company (a solvent extracted, hydrogenated paraffinic distillate containing less than 1 wt. % aromatics as analyzed using ASTM D 2007 clay-gel analysis). The blend did not meet the requirements of IEC 60296, ASTM D 3487 or BS 148:2003.
• a blend was prepared by combining the severely hydrotreated naphthenic distillate base oil shown in Table 2 with ERGONTM West Virginia P70N oil from Ergon Refining, Inc. (a hydrogenated paraffinic distillate containing 6.7 wt. % aromatics as analyzed using ASTM D 2007 clay-gel analysis), at 90/10 (Comparison Example 2) and 80/20 (Comparison Example 3) mixing ratios.
• the blends did not meet the requirements of IEC 60296, ASTM D 3487 or BS 148:2003.
• Comparison Examples 5-7 [0021] The severely hydrotreated naphthenic base oil shown in Table 2 (Comparison Example 5) and the solvent extracted, hydrogenated paraffinic distillates shown in Table 3 (Comparison Example 6) and Table 4 (Comparison Example 7) were individually tested to see if they met the requirements of IEC 60296, ASTM D 3487 or BS 148:2003. None did so.

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• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Organic Insulating Materials (AREA)
• Lubricants (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

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